I am
an observational cosmologist working in the fields of
reionization, galaxy evolution, cluster cosmology and
cosmic backgrounds. My group is active in science with
Planck, Euclid, Herschel and the Spitzer Space Telescope in
addition to a range of ground-based astronomical
observation facilities such as Palomar, Keck, CSO, CARMA
and ALMA. We are also involved in developing the next generation
of small explorer missions in collaboration with JPL.

Specifically, we are measuring the properties of
star-forming galaxies out to the highest redshifts, and in
conjunction with studies of gamma-ray burst number
densities and Type Ia supernovae, attempting to understand
fundamental properties of galaxies, such as how they grow
their stellar mass and metallicity, what is the stellar
mass function therein, when does dust begin to play a
significant role in their energetics and what fuels the
star-formation as a function of cosmic time. We are using
these measurements to provide, among other things, better
constraints on the reionization history of the Universe
between redshifts of 6 and 20 (the first billion years of
time), which is arguably the most important astrophysical
event since the Big Bang.

We
are also using objects at the extreme end of the dark
matter mass function, i.e. galaxy clusters, as a probe of
the structure of the Universe. By measuring cluster masses
over the last half of cosmic time (z<1) using galaxy
dynamics and the Sunyaev-Zeldovich effect, we can
constrain the equation of state of dark energy and
non-Gaussianity in the primordial density fluctuation
field, two quantities which are parametric representations
of the evolution of our Universe. Our most recent efforts have
measured spectral anomalies at the
10 parts per million in the cosmic microwave background to observationally constrain the existence of alternate universes with
physical properties different than our own.

Of
late, we have developed a mission concept to identify
the
electromagnetic counterparts of gravitational wave events that
are being detected by Advanced LIGO and Virgo.

We
attempt to be multiwavelength in our research, using the
observational facilities which are most appropriate to the
scientific question at hand and which minimizes the biases
that might result by only utilizing a single part of the
electromagnetic spectrum. We also make extensive use of powerful
computers to undertake Monte-Carlo simulations and tease out
signals from the data.